Knowledge of how the protein constituents of coated vesicles interact is required if we are to understand how the formation of a coated vesicle coordinates the morphological events of endocytosis or membrane flow with the biochemically specific events of receptor mediated uptake or intracellular protein sorting. Using coated vesicles isolated from mammalian tissues, binding assays, competition assays, and electron microscopy will be used to establish the specificity, affinity and structure of the connections that organize the coated vesicle proteins. Starting at the cytoplasmic side of the coated vesicle and extending eventually to the receptors that face the exoplasmic surface, proteins, polypeptides or fragments of polypeptides will be selectively stripped from the vesicles, and the ability of these components to reassociate with themselves in solution or to rebind to the selectively stripped vesicles in the presence of different ionic environments or protein factors will be measured. Because many cellular functions depend on coated vesicle function, perturbation of the normal protein interactions of coated vesicles can induce numerous disease states. Familial hypercholesterolaemia exemplifies one of the best documented diseases related to malfunction of receptor mediated endocytosis. Understanding coated vesicle function will also be important in controlling diseased states. Targeted cell killing using receptor dependent ligand uptake exemplifies one of the more obvious disease control strategies that will rely on knowledge of how coated vesicles function.